Overview: Kansas City has pieces in place to field an impressive young line consisting of franchise player Albert, second-year guard Allen, third-year center Hudson, fourth-year right guard Asamoah, and No. 1 pick Fisher. Off the bench can come power blocker Schwartz and 2012 third-round pick Donald Stephenson, an athletically gifted tackle. While this group remains in heavy transition with plenty to prove, the player-by-player assembly rivals the league’s top offensive lines. The pass blocking should -- and needs to -- take a big step forward under historically pass-first coach Andy Reid as Fisher upgrades on Eric Winston and Allen improves in year two.

Overview: Although Houston's 2012 front five drew strong marks across the board and returns every starter, this is not quite a question mark-free line. Brown and Myers remain top-notch starters, but both Smith and Newton are coming off knee surgery. Smith is 32 and entering his decline. Newton was the Texans' biggest up-front liability last season, getting overpowered in the run game and playing a big role in Arian Foster's career-worst 4.06 YPC average. Newton will be pushed by Harris and 2013 third-rounder Brennan Williams. Line play is still a plus for this offense, but the group has weaknesses and can no longer be considered among the NFL's elite.

Overview: All five starters return from a line that cleared the way for Washington to rank No. 5 in total offense. Critical to the Skins' 2012 run-blocking potency was durability, which is especially integral for the Shanahans' zone scheme because linemen move in unison. Williams, Lichtensteiger, Montgomery, and Chester all started 16-of-16 games. Polumbus started 15-of-16. So despite the fact that Lichtensteiger and Polumbus were not particularly effective individually, Washington still thrived with continuity. Some regression must be expected in that area. Depth pieces Compton (0 career starts), G/C Josh LeRibeus (0 career starts), and G/C Adam Gettis (0 career starts) are talented if untested reserves. While this offensive line is not a team weakness on the surface, the Skins still have a ways to go in pass pro and the depth is suspect at best.

Overview: The Eagles rank in the top half of the NFL's offensive lines because they're loaded with up-front talent. They just couldn't stay healthy last year. All-Pro Peters tore his right Achilles' twice and didn't play a down. Kelce lasted two weeks before tearing two knee ligaments. Herremans missed eight games with a dislocated foot. Watkins has chronic ankle problems and is a bust. Mathis was the only healthy starting lineman last season, and he is now recovering from ankle surgery. No. 4 pick Johnson is a fantastic fit for Chip Kelly's up-tempo offense, and this line has top-five potential, but the unit warrants a conservative ranking due to so many injury concerns.

Overview: The Saints believe in building their line from the inside out, stacking the interior with plus guard and center play and willing to field replacement-level talents at tackle. Grubbs, four-time All-Pro Evans, and UDFA steal De La Puente are the linchpins of New Orleans' trench unit. Strief is a former seventh-round pick out of Northwestern. Brown was a 2010 second-rounder but has been incredibly fragile in the NFL, battling back, hip, hamstring, and knee injuries over his first three seasons. He'll be pushed by raw but athletically freakish third-round rookie Armstead. While New Orleans' lack of left tackle clarity lowers its 2013 projection, this will likely be a quality O-Line. Drew Brees' lightning-quick decision making and delivery mask exterior protection flaws.

Overview: Effective line play went to waste last season as Mark Sanchez butt-fumbled away football games and Shonn Greene left enormous amounts of yards on the field. Gone are guards Brandon Moore and Matt Slauson, the former of whom remains on the street while the latter is competing for a job in Chicago. Colon-for-Slauson projects as a wash. Decorated wrestler and 50-game college starter Winters offers an impressive resume, but is a rookie. Ferguson and Mangold return as the nuts and bolts of the Jets' line, with improving power run-blocker Howard entering his second full season as a starter. While this front five has question marks, it projects as a plus run-blocking group for new feature back Chris Ivory. That's going to be vital, because the Jets must find ways to hide what inevitably will be one of the NFL's weakest passing attacks.

Overview: Line play was Indianapolis' single biggest 2012 weakness, so second-year GM Ryan Grigson attacked the front five in both free agency and the draft. Grigson shelled out a combined $49 million in max contracts to Thomas and Cherilus, who graded out as Pro Football Focus' No. 17 guard and No. 8 tackle, respectively. He then made 320-pound Thornton the 86th pick in the draft. Castonzo and Satele were already passable, if replacement-level starters, but this offensive line has experienced a major injection of talent. Ineffective and ousted incumbents G/T Joe Reitz (17 career starts), McGlynn (34 starts), and T/G Jeff Linkenbach (28 starts) now give the group an appearance of experienced, versatile depth. Easily a bottom-ten O-Line last season, the Colts suddenly look average at worst with a chance to creep into the top 15.

Overview: Coach Mike McCarthy implemented sweeping O-Line changes prior to OTAs, kicking former right-side starters Bulaga and Sitton over to the left, with Lang replacing Sitton at right guard and the right tackle job opened to a multi-player competition. Gone is 2012 free-agent bust Jeff Saturday, who was benched for Dietrich-Smith down the stretch last year. The aim of the Bulaga switch was to put Green Bay's most accomplished blocker on $130-million QB Aaron Rodgers' blindside. Incumbent starter Newhouse was a major liability, both in the run game and pass protection. The full effect of the up-front musical chairs is difficult to project, but benching Newhouse is addition by subtraction. The biggest camp battle will take place at right tackle between Newhouse, 2011 first-round pick Sherrod, Don Barclay, and rookie David Bakhtiari.

Overview: The Rams invested the majority of their free-agent dollars and draft picks into playmakers, but signed Long to create space on the field for the new ball carriers and catchers. Assuming Long plays closer to 2008-2010 form than 2011-2012, St. Louis will have upgraded two line positions, as Saffold kicks to right tackle, replacing street free-agent Barry Richardson. The interior remains suspect with Dahl showing signs of decline at age 32 and 2012 free-agent pickup Wells having undergone two right knee surgeries since last June, in addition to suffering a fractured foot. Wells is also 32 years old. As a fifth-round rookie, Watkins lasted one game before a season-ending ankle injury. Fourth-round rookie swingman Jones is coming off a Lisfranc fracture. This should definitely be the best offensive line of Sam Bradford's career, but there's little reason to believe it's a top 12-15 group, even if the Rams get better luck in terms of health.

Overview: O-Line talent isn't a strength of the Seahawks, but they absolutely max out their players’ abilities via position coach Tom Cable's tutelage and clear holes in the run game with a zone-blocking scheme. Hard-luck injuries wrecked Seattle's 2012 up-front continuity, as Carpenter missed nine games due to a knee injury and concussion, Moffitt was limited to six starts by elbow and knee woes, and Sweezy was brought along slowly as a former college defensive tackle. This line isn't star studded, but it's good enough and doesn't have a single projected starter above age 27. Whereas the Redskins can expect injury regression, Seattle ought to get it the other way around. Cable will pull production from this unit, and it can get better simply by staying healthy.

Overview: Re-proving that passing-based teams can overcome shaky line play, the 2012 Falcons did well to rank top eight in yards and top seven in points despite a sub-average front five. While Michael Turner's eroding skills deserve lots of blame, Atlanta ranked 29th in yards per rush (3.70) as the passing attack carried the offense. Baker is just a guy at left tackle. Reynolds was a mediocre right guard before a November back injury sent him to I.R. The 55th pick in last April's draft, Konz struggled mightily as a rookie guard. Right tackle Tyson Clabo was arguably Atlanta's most effective lineman, and he got cut in April. The right-side reins will fall on 2012 third-rounder Holmes, who played all of seven snaps as a rookie. With Clabo gone and longtime center Todd McClure retiring, Atlanta is getting younger up front. Only time can tell whether they'll be better.

You'll notice 2012 Run and Pass Block Rankings listed before each lineup projection. The first number is via Pro Football Focus. The second number is Football Outsiders' 2012 rating. While PFF and FO's data is relevant and valued, keep in mind the goal of this column is to project the effectiveness of 2013 NFL offensive lines, as opposed to rank them based solely upon what occurred last season.

The number in parentheses after each team name is that club's number of returning offensive line starters. The asterisk (*) denotes a new projected starter.

Overview: The 49ers are better in run blocking, but New England gets a big enough edge in the pass-blocking phase to put position coach Dante Scarnecchia's unit over the top. Despite ranking fourth in the league in pass attempts last season, the Patriots allowed the fifth fewest sacks in football. Pass pro is pretty important in an increasingly pass-first NFL. The Pats didn't lose any key line members and could receive a youthful, physical injection if 2011 fifth-round steal Cannon unseats incumbent right guard Connolly. Cannon is a nimble 6-foot-5 and 360 pounds. Solder and Vollmer were both top-17 offensive tackles in Pro Football Focus' 2012 ratings, while Wendell was a top-five center. Mankins, 31, is gunning for his fifth consecutive Pro Bowl berth.

Overview: San Francisco fields the most physical front five in football, evidenced by its consensus No. 1 run-block ranking in 2012. Only the Vikings and Redskins paved the way for better team yards-per-carry averages than the 49ers' 5.06 clip. All five starters return with Snyder (83 career starts) back for versatile depth after a failed stint in Arizona. With onetime first-round disappointment Davis turning a corner -- and still improving at age 23 -- the 49ers range anywhere from rock solid to elite at each position. Iupati is the group's strongest member. The returning All-Pro is the best drive-blocking left guard in the NFL and hasn't missed a start in his career. Boone gave the unit a new dimension in his first season as a full-time player in 2012, converting from tackle and actually grading out higher than Iupati in Pro Football Focus' individual guard ratings.

Overview:Peyton Manning's outstanding pocket management typically atones for up-front deficiencies, as was often the case in Indy behind O-Lines that would have been porous were anyone else playing quarterback. But Denver's front five was at the very least well above average last year and will get even better. Clady is the All-Pro mainstay and franchise player at age 26. Beadles and Walton both enter their fourth NFL seasons and are only 26 as well. (Walton missed all but four 2012 games and was replaced by Dan Koppen, who is currently a street free agent.) Franklin, 25, is rock solid in pass protection. Vasquez, 26, is another pass-blocker extraordinaire and adds mass to the unit at 6-foot-5 and 335 pounds. If healthy after fracturing his right fibula, Kuper is an ideal interior reserve with 78 games of starting experience, seeing action at both guard spots.

Overview: The names aren't flashy, but this quietly was about as good an offensive line as there was in the league last season, and doesn't lose a single starter. As a team, the G-Men ranked seventh in yards-per-carry average (4.55) despite several running back injuries, and allowed the fewest sacks in the NFL (20). Most critically, Beatty unseated Diehl on the blindside and emerged as an elite pass-blocking left tackle. Another consideration for Super Sub was guard Kevin Boothe, a returning starter who -- like Diehl -- I project to come off the bench, providing quality veteran depth. The assumptions here are mauling 2011 fourth-rounder Brewer beats out Diehl and 2013 first-rounder Pugh takes over at left guard, where he compares favorably to Andy Levitre. OT Brandon Mosley, 24, and OG Eric Herman, 23, are young reserve options with upside.

Overview: While the Buccaneers' 2012 offensive line ratings were not particularly strong, keep in mind they only got seven combined games from Nicks and Joseph, who form quite possibly the NFL's premier guard duo east of San Francisco. Nicks earned consecutive Pro Bowl trips before arriving in Tampa Bay last offseason, including a 2011 All-Pro berth. Joseph is a brute power blocker. They're healthy now. Despite injuries to arguably their best two linemen, the Bucs still allowed the third fewest sacks in football (26) and ranked 11th in yards-per-carry average (4.42). Depth is somewhat concerning, but there aren't five better starting O-Lines in the league.

Overview: An immobile rookie quarterback and injured tailback didn't help Cleveland's rate stats last season, but this is one of the most promising young lines in the league. Perennial All-Pro left tackle Thomas is the group's elder statesman at age 28. Pinkston, 25, Mack, 27, and Lauvao, 25, form an athletic and physical interior. Pinkston and Lauvao are backed up by Greco, a 28-year-old who can play both guard positions and blocked effectively in ten 2012 spot starts. Last year's 37th overall draft pick Schwartz was a top-three pass-protecting right tackle as a rookie, according to Pro Football Focus' ratings. If new coach Rob Chudzinski can work some Derek Anderson magic with Brandon Weeden, this Browns offense could take off in 2013.

Overview: This is another young, rising O-Line. Kalil, 23, Sullivan, 27, and Loadholt, 27, are Minnesota's elite up-front pieces, while improvement can be expected in 24-year-old Fusco's second season as a starter. Johnson, 29, was the weak link last year. He'll face competition from underrated sixth-round pick Jeff Baca and journeyman Berger (27 career starts). In 2011, the Vikings trotted out one of the NFL's poorest offensive lines. The ascension of Fusco and addition of Kalil turned the unit around. It's now a top-ten unit. Christian Ponder is running out of excuses.

Overview: McKinnie is marked as a "new starter" because Oher spent last season at left tackle, with Osemele on the right and Reid at left guard. Bobbie Williams, who was cut in March, started eight games at guard. Center Matt Birk has retired, giving way to 2012 top-100 pick Gradkowski. McKinnie took over at left tackle in January and performed admirably, surrendering just four quarterback hits across four playoff games. Including postseasons, McKinnie has made 22 starts on Joe Flacco's blindside over the past two years. The Ravens are 17-5 in those games, and Flacco has a combined 35:13 TD-to-INT ratio with a 8.16 YPA. Baltimore's offensive line is not quite elite, but it's an upper-echelon run-blocking unit and strong in pass pro whenever McKinnie is in good enough physical condition to start. 23-year-old Osemele has the potential to be a truly special player after neutralizing both Vince Wilfork and Justin Smith in the playoffs.

Overview: Outside of underwhelming center Cook, Cincinnati's front-five starters are rock solid and backed up by impressive depth. Collins is 27 years old with 18 career starts. He could start on many teams. G/T Travelle Wharton also received consideration for Super Sub. Wharton tore his ACL last year, but is healthy now and can play both left tackle and guard. Cook, returning from high ankle sprain surgery, will have to beat out incumbent seven-game starter Trevor Robinson. Whitworth and Smith each graded out as top-nine tackles in Pro Football Focus' 2012 ratings, while both Boling and Zeitler were top-25 guards, and now enter their second full seasons as starters. Despite this unit's modest run-blocking grades, it often made BenJarvus Green-Ellis look better than he is last year. The Bengals did allow the seventh most sacks in the league (46), though flatlining quarterback Andy Dalton deserves a lot of blame.

Overview: This is where ranking O-Lines gets tricky, because the Titans poured money (Levitre) and a top-ten pick (Warmack) into their most obvious up-front liabilities. The previous strength was tackle play, so it would seem the group has shored up its weaknesses. Theoretically, there is potential for Tennessee's line to leap into the top five. But Warmack is a rookie, Levitre is undersized and not a great run blocker, and right tackle Stewart has recovered more slowly than expected from a fractured right leg. The Titans indicated their concern by flirting with free agents Winston Justice and Eric Winston. Ultimately, a top-ten offensive line ranking is a positive and big jump from how Tennessee performed last year. Now they need Jake Locker to throw the football more accurately from the pocket and Chris Johnson to play harder on a down-to-down basis.

Overview: Kansas City has pieces in place to field an impressive young line consisting of franchise player Albert, second-year guard Allen, third-year center Hudson, fourth-year right guard Asamoah, and No. 1 pick Fisher. Off the bench can come power blocker Schwartz and 2012 third-round pick Donald Stephenson, an athletically gifted tackle. While this group remains in heavy transition with plenty to prove, the player-by-player assembly rivals the league’s top offensive lines. The pass blocking should -- and needs to -- take a big step forward under historically pass-first coach Andy Reid as Fisher upgrades on Eric Winston and Allen improves in year two.

Overview: Although Houston's 2012 front five drew strong marks across the board and returns every starter, this is not quite a question mark-free line. Brown and Myers remain top-notch starters, but both Smith and Newton are coming off knee surgery. Smith is 32 and entering his decline. Newton was the Texans' biggest up-front liability last season, getting overpowered in the run game and playing a big role in Arian Foster's career-worst 4.06 YPC average. Newton will be pushed by Harris and 2013 third-rounder Brennan Williams. Line play is still a plus for this offense, but the group has weaknesses and can no longer be considered among the NFL's elite.

Overview: All five starters return from a line that cleared the way for Washington to rank No. 5 in total offense. Critical to the Skins' 2012 run-blocking potency was durability, which is especially integral for the Shanahans' zone scheme because linemen move in unison. Williams, Lichtensteiger, Montgomery, and Chester all started 16-of-16 games. Polumbus started 15-of-16. So despite the fact that Lichtensteiger and Polumbus were not particularly effective individually, Washington still thrived with continuity. Some regression must be expected in that area. Depth pieces Compton (0 career starts), G/C Josh LeRibeus (0 career starts), and G/C Adam Gettis (0 career starts) are talented if untested reserves. While this offensive line is not a team weakness on the surface, the Skins still have a ways to go in pass pro and the depth is suspect at best.

Overview: The Eagles rank in the top half of the NFL's offensive lines because they're loaded with up-front talent. They just couldn't stay healthy last year. All-Pro Peters tore his right Achilles' twice and didn't play a down. Kelce lasted two weeks before tearing two knee ligaments. Herremans missed eight games with a dislocated foot. Watkins has chronic ankle problems and is a bust. Mathis was the only healthy starting lineman last season, and he is now recovering from ankle surgery. No. 4 pick Johnson is a fantastic fit for Chip Kelly's up-tempo offense, and this line has top-five potential, but the unit warrants a conservative ranking due to so many injury concerns.

Overview: The Saints believe in building their line from the inside out, stacking the interior with plus guard and center play and willing to field replacement-level talents at tackle. Grubbs, four-time All-Pro Evans, and UDFA steal De La Puente are the linchpins of New Orleans' trench unit. Strief is a former seventh-round pick out of Northwestern. Brown was a 2010 second-rounder but has been incredibly fragile in the NFL, battling back, hip, hamstring, and knee injuries over his first three seasons. He'll be pushed by raw but athletically freakish third-round rookie Armstead. While New Orleans' lack of left tackle clarity lowers its 2013 projection, this will likely be a quality O-Line. Drew Brees' lightning-quick decision making and delivery mask exterior protection flaws.

Overview: Effective line play went to waste last season as Mark Sanchez butt-fumbled away football games and Shonn Greene left enormous amounts of yards on the field. Gone are guards Brandon Moore and Matt Slauson, the former of whom remains on the street while the latter is competing for a job in Chicago. Colon-for-Slauson projects as a wash. Decorated wrestler and 50-game college starter Winters offers an impressive resume, but is a rookie. Ferguson and Mangold return as the nuts and bolts of the Jets' line, with improving power run-blocker Howard entering his second full season as a starter. While this front five has question marks, it projects as a plus run-blocking group for new feature back Chris Ivory. That's going to be vital, because the Jets must find ways to hide what inevitably will be one of the NFL's weakest passing attacks.

Overview: Line play was Indianapolis' single biggest 2012 weakness, so second-year GM Ryan Grigson attacked the front five in both free agency and the draft. Grigson shelled out a combined $49 million in max contracts to Thomas and Cherilus, who graded out as Pro Football Focus' No. 17 guard and No. 8 tackle, respectively. He then made 320-pound Thornton the 86th pick in the draft. Castonzo and Satele were already passable, if replacement-level starters, but this offensive line has experienced a major injection of talent. Ineffective and ousted incumbents G/T Joe Reitz (17 career starts), McGlynn (34 starts), and T/G Jeff Linkenbach (28 starts) now give the group an appearance of experienced, versatile depth. Easily a bottom-ten O-Line last season, the Colts suddenly look average at worst with a chance to creep into the top 15.

Overview: Coach Mike McCarthy implemented sweeping O-Line changes prior to OTAs, kicking former right-side starters Bulaga and Sitton over to the left, with Lang replacing Sitton at right guard and the right tackle job opened to a multi-player competition. Gone is 2012 free-agent bust Jeff Saturday, who was benched for Dietrich-Smith down the stretch last year. The aim of the Bulaga switch was to put Green Bay's most accomplished blocker on $130-million QB Aaron Rodgers' blindside. Incumbent starter Newhouse was a major liability, both in the run game and pass protection. The full effect of the up-front musical chairs is difficult to project, but benching Newhouse is addition by subtraction. The biggest camp battle will take place at right tackle between Newhouse, 2011 first-round pick Sherrod, Don Barclay, and rookie David Bakhtiari.

Overview: The Rams invested the majority of their free-agent dollars and draft picks into playmakers, but signed Long to create space on the field for the new ball carriers and catchers. Assuming Long plays closer to 2008-2010 form than 2011-2012, St. Louis will have upgraded two line positions, as Saffold kicks to right tackle, replacing street free-agent Barry Richardson. The interior remains suspect with Dahl showing signs of decline at age 32 and 2012 free-agent pickup Wells having undergone two right knee surgeries since last June, in addition to suffering a fractured foot. Wells is also 32 years old. As a fifth-round rookie, Watkins lasted one game before a season-ending ankle injury. Fourth-round rookie swingman Jones is coming off a Lisfranc fracture. This should definitely be the best offensive line of Sam Bradford's career, but there's little reason to believe it's a top 12-15 group, even if the Rams get better luck in terms of health.

Overview: O-Line talent isn't a strength of the Seahawks, but they absolutely max out their players’ abilities via position coach Tom Cable's tutelage and clear holes in the run game with a zone-blocking scheme. Hard-luck injuries wrecked Seattle's 2012 up-front continuity, as Carpenter missed nine games due to a knee injury and concussion, Moffitt was limited to six starts by elbow and knee woes, and Sweezy was brought along slowly as a former college defensive tackle. This line isn't star studded, but it's good enough and doesn't have a single projected starter above age 27. Whereas the Redskins can expect injury regression, Seattle ought to get it the other way around. Cable will pull production from this unit, and it can get better simply by staying healthy.

Overview: Re-proving that passing-based teams can overcome shaky line play, the 2012 Falcons did well to rank top eight in yards and top seven in points despite a sub-average front five. While Michael Turner's eroding skills deserve lots of blame, Atlanta ranked 29th in yards per rush (3.70) as the passing attack carried the offense. Baker is just a guy at left tackle. Reynolds was a mediocre right guard before a November back injury sent him to I.R. The 55th pick in last April's draft, Konz struggled mightily as a rookie guard. Right tackle Tyson Clabo was arguably Atlanta's most effective lineman, and he got cut in April. The right-side reins will fall on 2012 third-rounder Holmes, who played all of seven snaps as a rookie. With Clabo gone and longtime center Todd McClure retiring, Atlanta is getting younger up front. Only time can tell whether they'll be better.

Overview: You'd never know it because of Ryan Fitzpatrick's annually lackluster production, but Buffalo fielded one of the league's most underrated lines during Chan Gailey's tenure. In Gailey's Pistol Spread, the Bills got the ball out quickly and ran efficiently, ranking fifth in yards per carry in 2011 (4.91) and fourth in 2012 (5.02). Gailey spread the field with four and five wideouts, creating advantageous run matchups. Unfortunately, Buffalo lost top lineman Andy Levitre this offseason, and how the remaining players will transition to rookie coach Doug Marrone's scheme remains to be seen. While Fitzpatrick was error prone and lacked starting-caliber arm talent, his quick release masked up-front flaws that may be exposed with painfully-raw rookie E.J. Manuel under center.

Overview: Although Kalil has been Carolina's stalwart center since breaking into the starting lineup in 2008, he is listed as a "new starter" here because he missed all but five games last season with a Lisfranc fracture. Hangartner slid to center and guard Jeff Byers was forced onto the first string with largely disastrous results. Jonathan Stewart and DeAngelo Williams slugged their way to a combined 4.03 YPC average while Cam Newton's sack rate rose from 6.3 to 6.9 percent of his dropbacks. Kalil's return will help the up-front cause, but Hangartner is still penciled in at right guard and Bell graded out 60th-of-80 qualifying tackles in Pro Football Focus' 2012 ratings. Cap-strapped Carolina didn't have financial means to address the line this offseason. The only notable reinforcement is fourth-round guard Edmund Kugbila, a project from Valdosta State.

Overview: After selecting DeCastro in last year's first round and Adams in the second, the Steelers were commonly billed as post-draft "winners" with the sudden potential to field one of the league's top young lines. Instead, DeCastro blew out his knee in the preseason and made three starts. Adams was beaten like a drum, coughing up seven sacks in ten games. The Steelers ranked 28th in YPC average (3.73) and Ben Roethlisberger got injured again. The offensive line remained their Achilles' heel. While a healthy dose of talent returns, this is a group to be viewed with skepticism until it makes tangible on-field strides. The unit is also starving for depth, as Beachum (five career starts) and swinging-gate Guy Whimper (22 starts) are the top reserves.

Overview: The presence of Pro Bowl-caliber left tackle Monroe, healthy return of 2011 rookie starter Rackley, and addition of Joeckel give Jacksonville's offensive line some credibility, even if it remains a probable bottom-ten unit. Longtime center Meester turned 36 in March and Nwaneri is recovering from knee surgery. Rackley missed all of last season with a severe high ankle sprain that required surgery. While this line should be better now, it's hard to forget that Jacksonville allowed the third most sacks in football (50) last season and ranked 24th in yards per rushing attempt (3.82). Still, there are reasons to believe this front five can at least be serviceable enough to give the Jags a puncher's chance of playing competitive offense, assuming they keep Maurice Jones-Drew healthy and somehow scrounge together passable quarterback play.

Overview: Detroit's lofty 2012 pass-block grades from Football Outsiders and Pro Football Focus were largely attributable to tackle play. Right tackle Gosder Cherilus, who left for greener pastures in Indianapolis, was PFF's No. 5 pass-blocking tackle. Long-underappreciated left tackle Jeff Backus came in a respectable 26th. Replacing Cherilus will be the winner of a camp battle between Fox (26 NFL snaps) and journeyman Hilliard. The Lions preferred Reiff's short arms and average athleticism at guard, but will have to stick him at left tackle after Eric Fisher and Lane Johnson went before their pick at No. 5 overall. Raiola, 34, had to take a massive pay cut to stay in Detroit. Warford projects as a good player in time, but he's an unproven third-round rookie. Sims is the Lions' best lineman. This revamped front five is likely to struggle for consistency.

Overview: Game watchers know Tony Romo played last season under constant siege. Because Romo is such an extraordinary pocket manipulator with instinctive feel for the pass rush, Dallas managed to rank a middling 16th in the league in sacks allowed (36) despite genuinely poor line play. They were 30th in yards-per-carry average (3.56). Free is the most overpaid offensive lineman in football and could lose his job to Parnell, if he doesn't lose his roster spot altogether. Bernadeau has never been an effective blocker, forming one of the league's worst right sides. Smith is an immense talent, but was a disappointment in his first year on the blindside. Lone new face Frederick was an obvious reach in the first round. At best, this was a well below-average line in 2012 and there is little or no reason to think it made significant offseason gains.

Overview: After an abysmal year of line play, GM Phil Emery used his first-round pick (Long) and largest free-agent signing (Bushrod) to address the front five. The Bears need lots of help, because they're gearing up to play pass-first offense under rookie coach Marc Trestman. If the Bushrod addition works as planned, Chicago will upgrade two positions with the move, as 24-year-old Webb kicks to the other side. The team played 2012 musical chairs at right tackle, with Carimi and journeyman Jonathan Scott both failing. While the unit looks improved on paper, that’s not saying very much, and the Bears still lack a top-end starter at any of the five spots. This O-Line remains a work in progress.

Overview: GM Jeff Ireland poured offseason resources into linebacker, defensive end, cornerback, receiver, and tight end. Relatively speaking, he invested pennies into franchise QB Ryan Tannehill's protection after a below-average year of line play. The lone significant additions were Clabo and Louis, the former of whom hasn't played in a zone scheme like Miami's in nearly a decade. Louis is coming off a late-season ACL tear. While Mike Wallace, Brian Hartline, and Brandon Gibson account for roughly $100 million in max-contractual worth, Louis and Clabo are owed just over $5 million. After whiffing on left tackle targets Jake Long, Branden Albert, and Bryant McKinnie, the Fins will settle for 2012 turnstile Martin on Tannehill's blindside. It's a high-risk projection. Martin got lit up in pass pro as a rookie. Head scratchingly, O-Line was the one part of Miami's roster Ireland allowed to get worse amid free-agency binge spending and stockpiling of draft picks acquired by trading away two of his best players (Brandon Marshall, Vontae Davis).

Overview: The Raiders will undergo their second O-Line overhaul in as many seasons, transitioning from a zone to power scheme. Oakland ranked 27th in 2012 YPC average (3.78), unable to clear holes without committing holding penalties. Were the struggles due more to scheme or the blockers themselves? Suppose we'll find out this year. The best lineman -- by far -- is Veldheer, who pass blocked well enough to help Oakland allow just 27 sacks, tying New England for the NFL's fifth lowest total. That was despite the league's least mobile quarterback (Carson Palmer). Entrenched starters are Veldheer, Wisniewski, and probably second-round rookie Watson, a questionable fit for the new scheme because he's a finesse right tackle. Barnes, Nix, Bergstrom, and 2012 free-agent bust Mike Brisiel -- another poor scheme fit -- will vie for the other two positions. In all likelihood, Oakland's line play will continue to be a negative, even if it improves slightly this year.

Overview: The Cardinals fielded the NFL's worst 2012 O-Line, and it wasn't close. They couldn't pass or run block. New GM Steve Keim and coach Bruce Arians have a long way to go to make this front five competitive, but at least they're trying. Turnstile left tackle D'Anthony Batiste was not retained, and right guard liability Adam Snyder was cut. The Cards have pursued ex-Arians understudy Max Starks in free agency. While Cooper helps, he can't do it on his own. Back from his torn triceps, Brown ranked 75th-of-76 tackles in Pro Football Focus' 2011 pass-block ratings. Massie improved as his 2012 rookie year progressed, but he was 74th-of-80 tackles. Colledge and Sendlein are below-average starters. Potter is a viable swing lineman, but stretched mightily on the first team. It'll probably take another year for this unit to reach mediocrity.

Overview: The Chargers are a good sleeper for the No. 1 pick in the 2014 NFL draft because they can't protect their quarterback, and can't rush other teams' quarterbacks. GM Tom Telesco's first season is going to be a long one. Both projected starting tackles are heavy-footed waist benders who will get destroyed by Von Miller, Justin Houston, and Tamba Hali in the AFC West. The Chargers openly confirmed their concern in Dunlap by flirting with Bryant McKinnie and Max Starks. Hardwick, entering his age-32 season, graded out 31st-of-36 centers in Pro Football Focus' 2012 ratings. The club has moved annual pass-protection sieve Clary from right tackle to guard and will pray he plays better there. Journeyman Rinehart is on his third NFL team in six seasons. He'll compete with Troutman at left guard. The 2012 Chargers ranked 31st in yards-per-carry average (3.55) and coughed up the fourth most sacks in the NFL (49). Philip Rivers has absorbed hits to the point that he now sees ghosts in the pocket. Expect more of the same in 2013.